Method and apparatus for drilling underwater wells



July 5, 1966 N. E. MONTGOMERY ET AL METHOD AND APPARATUS FOR DRILLINGUNDERWATER WELLS Filed May 28, 1965 FIG. I

6 Sheets-Sheet 1 INVENTORSI N. E. MONTGOMERY F. F. MARTIN BY: HJM

THEIR AGENT July 5, 1966 N. E. MONTGOMERY ET AL 3,259,198

METHOD AND APPARATUS FOR DRILLING UNDERWATER WELLS 6 Sheets-Sheet 2.Filed May 28, 1963 FIG. 4

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FIG. 3

INVENTORS'.

N. E. MONTGOMERY F. F. MARTIN BY: HJ

T EIR AGENT July 5, 1966 N. E; MONTGOMERY ET AL 3,259,198

METHOD AND APPARATUS FOR DRILLING UNDERWATER WELLS Filed May 28, 1963 6Sheets-Sheet 5 VIII/4 5.03%

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INVENTORSI N. E. MONTGOMERY F. F MARTIN EIR AGENT BYZ y 1966 N. E.MONTGOMERY ETAL 3,259,198

METHOD AND APPARATUS FOR DRILLING UNDERWATER WELLS Filed May 28, 1963 6Sheets-Sheet 4 FIG. 7

INVENTORS! N. E. MONTGOMERY F. F. MARTIN EIR AGENT y 1966 N. E.MONTGOMERY ET AL 3,259,198

METHOD AND APPARATUS FOR DRILLING UNDERWATER WELLS Filed May 28, 1963 6Sheets$heet 5 FIG.

INVENTORS'.

N. E. MONTGOMERY F. F. MARTIN BY: 6 H 72 THEIR AGENT FIG.

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July 5, 1966 N. E. MONTGOMERY ET AL 3,259,198

METHOD AND APPARATUS FOR DRILLING UNDERWATER WELLS Filed May 28, 1963 6Sheets-Sheet 6 Thad? FIG.

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lNVENTORSi N. E. MONTGOMERY F. F. MARTIN BY. $3

EIR AGENT United States Patent 3,25,198 METHOD AND APPARATUS FQRDRlILLlNG UNDERWATER WELLS Norman E. Montgomery, Metairie, and Fines F.Martin, New Orleans, La, assignors to Shell Oil Company, New York, N.Y.,a corporation of Delaware Filed May 28, 1963, Ser. No. 283,844 13Claims. (Cl. 175-7) This invention relates to the underwater drilling ofoil and gas wells and pertains more particularly to methods andapparatus for drilling underwater wells at deep-water locations from afloating vessel wherein it is essential that a drilling fluid becirculated down through a drill string to the bottom of the well andreturn to the vessel during drilling operations.

During recent years, the continued search for oil has resulted indeveloping methods and apparatus for drilling underwater wells atlocations where the water may range from 100 to 660 feet in depth. Inthese locations it is customary to position a wellhead at a considerabledistance below the surface of the water, preferably on the ocean floor,so that it is not a hazard to navigation of ships in the area.

During the drilling of a well it is generally necessary to employ adrilling fluid which is circulated down through a rotating drill stringand through the drill bit at the bottom thereof in order to flush theearth-formation cuttings away from the bit and transport them up theoutside of the drill string and out of the well. In starting to drill awell in the ocean floor, the drilling fluid employed is normally saltwater and no attempt is made to circulate the salt water into and out ofthe well and back to the vessel. Instead, as the salt water drillingfluid comes out of the well it is allowed to mix with the ocean.However, after drilling operations have continued for some time, it isnecessary to change the drilling water composition from plain salt waterto one containing clay and various chemical additives in order to givethe drilling fluid the desired characteristics required at theparticular location. In drilling through formations where gas or oilpressure may be encountered in a substantial amount, it is generallynecessary to weight the drilling fluid by adding barites to the fluid.

Since drilling fluids may often be quite expensive and cost manythousands of dollars for a single well, it is essential that drillingfluid loss be reduced to a minimum; Previously, in drilling underwaterwells from a floating vessel on the surface of the water, drilling fluidhas been returned to the vessel in one of two manners.

In one system, in addition to the drill string extending between thevessel at the surface of the water and a wellhead on the ocean floor, aflexible hose is connected to the wellhead, preferably to one sidethereof, so that when drilling fluid comes up the well outside the drillstring to the wellhead it flows into the flexible hose and is forced upthe hose to the vessel. While this method of drilling is satisfactory inshallow water locations at most offshore areas, in some areas wherestrong underwater currents exist, the flexible drilling fluid returnhose is whipped back and forth and often against either the rotatingdrill string or the wellhead structure in a manner such that it wearsout quickly and ruptures. When using this system in deep water location,one is faced with the problem of providing a hose having sufiicientstrength so that it will not pull apart when a considerable length ofit, say 500 feet, is suspended from the vessel at the surface of thewater. The hose must be fairly large and have a bore sufficient so thatearth cuttings can be circulated up through the hose with ut cloggingit. It is realized that any hose of this type can be stren thened byputting steel wire in its structure but this complicates the handling ofthe hose Patented July 5, 1966 on the vessel or on hose reels because ofthe stiffness of the hose. Another disadvantage of using hoses forreturning drilling fluid and earth cuttings to the surface is that thehose may temporarily kink in a manner such that the cuttings in the hosewould form a plug at the kink which could not readily be circulated outwhen the hose was straight.

In order to overcome many of these problems in water depths over feet, asecond Well drilling system was adopted which made use of a marineconductor pipe which is a large-diameter pipe, say 16 inches or more indiameter which extends from an underwater wellhead to a vessel on thesurface of the water. The lower end of the marine conductor pipe isnormally releasably latched to the top of the wellhead while the upperend of the marine conductor pipe is secured to the vessel at thesurface, preferably by means of constant tension hoists so as tocompensate for the rise and fall of the vessel relative to theunderwater wellhead. In carrying out drilling operations with thisapparatus utilizing a marine conductor pipe, after the wellhead waspositioned on the ocean floor the marine conductor pipe was eitherstripped down over the drill string extending from the wellhead to thevessel, or the marine conductor pipe was lowered with the aid ofsuitable guide means into the latching position on the wellhead and adrill string was subsequently run down through the marine conductorpipe, the wellhead and into the well.

A marine conductor pipe of several hundred feet of large diameter pipepossessed considerable weight and it is a problem to support the weightof this pipe during drilling operations. It has been found undesirableto attempt to support the weight of this pipe on the underwater wellheadstructure so all or most of the weight of the marine conductor pipe iseither supported by means of constant tension hoists secured to itsupper end or by means of buoyancy tanks secured to the outside of themarine con-ductor pipe, or a combination of the two solutions. The useof a marine conductor pipe possesses certain disadvantages. Because ofthe large diameter of the pipe its flexibility is much less than that ofa drill pipe and hence the drilling vessel on the surface of the waterto which the top of the marine conductor pipe is connected must bemaintained in a relatively stationary manner against movement caused bywind and wave forces. If the vessel was allowed to move off position toofar, that is, to an extent that the marine conductor pipe is not in asubstantially vertical position between the vessel and the underwaterwellhead, the marine conductor pipe may be permanently bent or ruptured.

Another drawback in using large diameter marine conductor pipes is thatthey contain substantially more drilling fluid than say a drill pipe.Thus, in drilling in 300 feet of water, a 20-inch diameter marineconductor pipe extended from the wellhead to the vessel at the surfacewould have a 20-inch column of drilling mud contained inside the pipe.When drilling in high pressure formations, this drilling mud may beweighted to as much as 17 or 18 pounds per gallon or 127 to pounds percubic foot. In the event that the top of a marine conductor pipecontaining a heavy mud of this type starts to bend near the surface ofthe water, the action of gravity causes it to bend further thusendangering the pipe in the drilling operation. While thesedisadvantages have been overcome to date by the use of larger hoses fromthe vessel or larger buoyancy tanks on the marine conductor pipe inorder to keep the latter in a substantially vertical position duringdrilling operations, these remedies are not practical when drilling indeep water locations where the water is from 1000 to 5000 feet deep.

In deep water locations it would be necessary to increase the size ofthe buoyancy tanks on the marine conductor tanks to an extent that theybecome quite enormous, thus possessing large areas against which waveforces and underwater currents could act in a manner causing the marineconductor pipe to deflect from its normally vertical position within thewater. At the same time if constant tension hoists were to be employedto apply tension to the top of the marine conductor pipe from thevessel, larger and more buoyant vessels would have to be employed aswell as vessels having larger hoists.

It is therefore a primary object of the present invention to provide amethod and apparatus for drilling underwater wells at deep-waterlocations where it is necessary to cirulate a drilling fluid from avessel on the surface of the water down into the well and back to thevessel.

A further object of the present invention is to provide apparatus fordrilling underwater wells wherein the fluid circulation system betweenthe vessel and the well is more flexible than a marine conductor pip andhas greater strength and rigidity than a flexible hose.

Another object of the present invention is to provide apparatus fordrilling underwater wells in deep-water locations wherein the fluidcirculation system between the vessel and the underwater well is lighterthan a marine conductor pipe so that it is more readily supported duringdrilling operations with its upper end at the vessel.

Still another object of the present invention is to provide appartus fordrilling in deep-water locations wherein the circulation systemextending between the vessel and the wellhead is of a small size so thata minimum area is exposed to wave forces and underwater currents tendingto deflect the system from the vertical.

A further object of the present invention is to provide apparatus fordrilling deep-water wells from a vessel with a circulation system to anunderwater wellhead which extends into and is slidably movable in thetop of the wellhead so as to eliminate the need for a telescopingsection of marine conductor pipe adjacent the vessel.

It is also an object of the present invention to provide apparatus fordrilling underwater wells in deep-water locations wherein thecirculation pipe system extending between the vessel and the wellheadpasses ntirely through the wellhead and depends within the Well so thatthe weight of the circulation system in the well applies a tension tothat portion of the circulation pipe, system between the wellhead andthe vessel which tends to maintain the circulation pipe system in asubstantially straight line between the wellhead and the vessel.

A further object of the present invention is to provide apparatus fordrilling underwater wells at deep-water locations wherein thecirculation pipe system extending between the vessel and the underwaterwellhead possesses a relatively small volume of drilling mud at any timethus minimizing any tendency for the circulation pipe system to bedeflected from the vertical.

Still another object of the present invention is to pro vide apparatusfor drilling an underwater well at deepwater locations when it isdesired to continuously core.

the earth formation being penetrated by the drill bit during thedrilling of the well.

These and other objects of this invention will be understood from thefollowing description taken with reference to the drawing, wherein:

FIGURES 1 through 6 are diagrammatic views taken in partial longitudinalcross section illustrating a floating vessel positioned over a drillinglocation during the seqential steps of starting to drill an underwaterwell, installing a foundation pile or a casing in the well, cementingthe foundation casing in the well, continuing drilling the well throughdeeper formations, running another string of casing into the well, andapplying one form of a guide element to maintain contact with the well.

FIGURE 6A on page 3 of the drawing is a longitudinal view taken inpartial cross section illustrating one form of a drill bit in accordancewith thepresent invention adapted to support the upper end of a guideelement therefrom;

FIGURES 7, 8 and 9 are three longitudinal views taken in partial crosssection illustrating three dilferent forms of an underwater drillingwellhead together with guide means for positioning various wellheadcomponents and/or the lower end of a drill string or casing string inaxial alignment with the foundation casing in the well;

FIGURE 10 is a longitudinal view taken in partial cross sectionillustrating a fluid circulation swivel head mounted at the top of adual conduit kelly for use in accordance with the present invention;

FIGURES 11 and 12 are longitudinal views taken in partial cross sectionof two forms of pipe couplings to be employed in a dual conduit drillstring of the present invention;

FIGURE 13 is a longitudinal view of the lower end of a drill string inaccordance with the present invention illustrating the circulation pathof drilling fluid;

FIGURE 14 is a longitudinal view taken in partial cross section,illustrating another arrangement of drill collars at the lower end ofthe dual conduit drill string with fluid discharge pores beingpositioned above a telescoping section in the drill string;

FlGURE 15 is a longitudinal View taken in cross section of a dualconduit telescoping section of drill string;

FIGURE 16 is a longitudinal view taken in cross section of a cross oversub adapted for use in a dual concentric type drill string; and

FIGURE 17 on page 2 of the drawings is a longitudinal view of anotherform of concentric drill string and bit.

Referring to FIGURE 1 of the drawing, a drilling vessel, barge orplatform 11, of any suitable floating or floatable type is illustratedas floating on the surface of a body of water 12 while beingsubstantially fixedly positioned over a preselected well location bysuitable vessel positioning means well known to the art, or by beinganchored to the ocean floor 13 by anchor lines 14 and 15 running toanchors (not shown). Equipment of this type may be used when carrying onwell drilling operatrons or well workover operations in water varyingfrom to 5000 feet or more in depth. The drilling vessel 11 is equippedwith a suitable derrick 16 containing a fall line system 17 whichincludes a suitable hoist (not shown), traveling block 19, and asuitable hook and swivel or other connector means 20 adapted to beconnected to the top of a kelly 21 at the upper end of a drill pipe 22during well-drilling operations and being adapted to circulate adrilling fluid therethrough in a manner well known to the art. Thevessel 11 is also provided with other auxiliary equipment needed duringwell-drillingoperations, such, for example, as a rotary .table 23positioned on the operating deck, a mud pit or tank 24-, etc. Thederrick 16 is positioned over a drilling slot or well 25 which extendsvertically through the barge in a conventional manner. When usingdrilling equipment of the present invention, a slot 25 in the vessel 11may be either centrally located or extend in from one edge.Alternatively, drilling operations may be carried out over the side ofthe vessel without the use of a slot. For example, the drilling vesselmay be provided with a deck portion which overhangs th hull of thevessel.

The drill string 22 preferably includes a conventional telescoping joint26 in its length to compensate for the rise and fall of the vessel 11relative to the drill string 22. The drill string 22 also includes adrill bit 27 at its lower end which is provided with one or moreopenings for circulating fluid such as drilling mud therethrough. Atleast one opening in the bit is positioned therein so that drilling mudcan be circulated through the bit.

The length of the telescoping joint or bumper sub 26 is selected to bepreferably slightly greater than the expected rise and fall of thevessel so that the drill bit 27 will remain in drilling contact with thebottom of the well or hole 28 regardless of weather conditions at thesurface. The telescoping joint 26 may be positioned near the upper endof the drill string at the start of the drilling operation, as shown inFIGURE 1, or it may be located just above the drill bit 27 or drillcollars in the form of a bumper sub in a manner well known to the art.The bumper sub may have a telescoping length of say 5 feet, or more thanone bumper sub may be employed if desired. When using a number of drillcollars at the bottom of the drill string and above the drill bit, it isoften desirable to put the bumper sub 26 in the drill string below atleast one of the drill collars so that the weight of the drill collarabove the telescoping joint or bumper sub 26 may be utilized totelescope the sub toward its contracted position rather than letting theweight of the drill string set down on the sub from above. Although forease of illustration the drill string 22 is shown as a unitary length ofpipe, it is well known that a pipe string or drill string used in welldrilling operations is made up by threadedly connecting together severalshort (say feet) sections of pipe to make up a pipe string of thedesired length.

FIGURE 1 illustrates the start of a method by which an underwater wellis drilled from a floating vessel 11 positioned at the surface of thewater 12. In starting a well, the drilling vessel 11 is first positionedat a selected drilling location. The drill string 22 having a bit 27 atthe lower end thereof is lowered from the vessel into contact with theocean floor. Several of the bottom sections of the pipe forming thelower end of the drill string 22 may be thick-walled in the form ofdrill collars, if desired. The drill string 22 includes a kelly section21, of square, hexagonal, or other non-round cross section, which isslidably positioned in the bushing of the rotary table 23 in a mannerwell known to the art. Drilling is commenced by the rotary table beingdriven by suitable motor means to rotate the kelly section 21 and thedrill string 22 connected to its lower end. As the drill bit 27 isdrilled into the ocean floor, the kelly section 21 slides down throughthe bushing in the center of the rotary table 23 until the upper end ofthe kelly reaches the table 23. During the drilling operation a drillingfluid is circulated, by means of a pump 30, through hose 31 and into thetop of the kelly 21 through swivel 20. From there the drilling fluid isforced down through the drill string 22 and out discharge ports in thebit 27. After being discharged from the bit 27, drilling fluid moves upthe borehole 28 and at the start of drilling operations is discharged tothe ocean. Thus, at the start of drilling operations the drilling fluidis normally sea water which is sufiicient to flush the earth formationcuttings from the well 28. As

I drilling progresses, additional sections of drill pipe are added tothe drill string 22 below the kelly section 21 in a manner well known tothe art.

In starting a well, the drill string 22 is preferably pr'ovided with ahole opener or collapsible bit 32 (FIGURE 1) of a type well known to theart so that a hole 28 can be drilled in the ocean floor 13 large enoughto receive a large-diameter foundation casing 33 (FIGURE 2) while at thesame time being adapted to be pulled up through the casing 33. In FIGURE2 a well foundation casing 33, preferably having a wellhead base 34secured near the top thereof, is lowered into the well 28 by sliding orstripping it down over the drill pipe 22. The foundation casing 33 andthe wellhead base 34 may be lowered into position by means of aplurality of cables 35 and 36 running off of hoists 37 and 38. The lowerends of the cables 35 and 36 may be secured within vertically extendingguide columns 39 and 40 secured to the wellhead base 34. Thus, thelowering cables 35 and 36 form guide lines for lowering other equipmentto the ocean floor in axial alignment with the foundation casing 33. Inorder to maintain a predetermined tension from the guide lines casing 33has been inserted in the well 28, as illustrated a in FIGURE 2, thedrill string 22 can be withdrawn from the well and the remaining lengthof the foundation casing 33 can be lowered into the well without anyguide apparatus.

If desired, the drill string 22 (FIGURE 2) can be left in the well untilthe foundation casing 33 is in place so that cementing operations can becarried out through the drill string. If it is not desired to cementthrough the drill string, a cementing pipe string 41 (FIGURE 3) may berun down into the foundation casing 33 so that cementing operations canbe carried out in the normal manner by pumping cement down through thepipe string 41 and foundation casing 33 and thence upwardly in theannular space between the outside of the foundation casing 33 and theinner wall of the borehole 28.

It is understood that the underwater well may be started by othermethods well known to the art. Thus, in another method a large-diameter(say 30 inch) pipe is driven or forced and/ or jetted into the oceanfloor from a floating vessel at the surface. Guide lines are secured tothe upper end of the pipe for guiding a drill bit and its carrier intothe pipe for drilling a hole in the ocean floor. Subsequently a wellheadfoundation pile or casing and a casinghead are lowered along the guidelines into position in the well after the drill string and bit have beenwithdrawn.

Prior to continuing well-drilling operations, ablowout preventer 42connected to a wellhead connector 43 is run down suitable guideequipment, such as guide lines 35 and 36 (FIGURE 4), and positioned ontop of the foundation casing 33. The upper end of the foundation casing33 is generally formed in a manner to provide a casinghead 44. Theblowout preventer 42 and the wellhead connector 43 are remotelyactuatable from the vessel 11 in a manner Well known to the art while aremovable sealing unit 45 is provided at the top of the blowoutpreventer 42 for sealing around the drill string 46. At this stage ofthe operation, the drilling fluid being used may have expensivechemicals or other additives contained therein so that it is essentialthat drilling fluid being circulated down to the well be returned to thevessel afterwards. In order to do this the drill string 46 employed isone having multiple conduits through its entire length.

Typical drilling wellhead assemblies are illustrated in more detail inFIGURES 7, 8 and 9. Preferably, each component such as blowout preventer42, wellhead con-. nector 43 or sealing unit 45 to be lowered from thevessel 11 at the surface down into an aligned and seated position on topof the casinghead 44, is provided with suitable guide means, such asguide arms 47 and 48 which are fixedly secured to blowout preventer 42.The outer ends of the guide arms 47 and 48 are provided with a guideelement, such as 49, which is latched onto the guide line 36 at thevessel so as to surround guide line 36 and be mounted in slidingengagement therewith. The guide arm 48 moves down a slot 50 extendingthrough the wall of the guide column 40 in a direction extendingradially from the axis of the foundation casing 33. The blowoutpreventer 42 is provided with hoses 51 and 52 whereby hydraulic pressurefluid can be pumped from the vessel at the surface to open or close theblowout preventer 42. In the event that a bag-type blowout preventer isemployed, only one pressure hose 51 may be needed. A nipple or shortpipe section 53 at the top of the blowout preventer 42 is of a size tobe received within the bore 54 of the sealing unit 45. Additionally thethroughbore extending axially within the nipple 53 and the blowoutpreventer 42 is of a size to permit passage of the drill bit 55 at thelower end of the drill string 46. A- resilient annular seal 56 withinthe sealing unit 45 seals against the drill string 46 in a fluidtightmanner so as to prevent the escape of drilling fluid therefrom. Anysuitable type of seal may be employed. While a hydraulically-actuatedseal 56 may be preferable in some situations, in general, a static sealof proper design will be satisfactory. The bore through the sealing unit45 is small enough at one portion thereof so that when the drill bit ispicked up out of the well and pulled up to the vessel it will pull thesealing unit 45 along with it up the guide line 35 and 36.

In FIGURE 7 the weight of the sealing unit 45, or weighting elementsadded thereto, holds the unit on the landing nipple 53 at the upper endof the blowout preventer, while in FIGURE 8 the sealing unit 45 ispositively locked to the blowout preventer 42. It is realized that theunit of FIGURE 7 could also be provided with locking dogs as in FIGURE8. In the arrangement shown in FIGURE 8 the sealing unit 45 is providedwith a downwardly-extending mandrel 57 having latching grooves 58 formedin the outer surface thereof. The mandrel 57 is of a diameter to fitwithin the bore 59 of a latch-down unit 60 which is formed on or boltedto the blowout preventer 42. The latching unit 60 may be of any suitabledesign such as one being provided with a series of latching dogs 61adapted to be moved inwardly so that they extend into the bore 59 of thelatching unit and engage the grooves 58 of the mandrel 57 when thelatter is positioned in the latching unit 60. The latching dogs 61 maybe actuated by a vertically movable piston 62 which is moved up or downinto unlocking or locking position by the application of a pressurefluid through pressure hoses 63 and 64 which run to the vessel. A seal65 may be provided on the mandrel 57 to form a fluidtight seal betweenthe mandrel 57 and the latch-down unit 60. It is to be understood thatthe drill string 46 is adapted to be rotated and moved axially withinthe seal 56 of the sealing unit 45 while at the same time the seal 56forms a substantially fluid-tight seal around the outside of the drillstring 46.

The drilling wellhead assembly of FIGURE 9 is similar to that describedwith regard to FIGURE 8 except that instead of having hydraulic hoses51, 52, 63 and 64 (FIG- URE 8) running down to the wellhead to actuatethe latch-down unit 60 and the blowout preventer 42, the wellheadassembly is provided with a self-contained actuator unit 66. Thisactuator unit 66 may be an electrical or electro-hydraulic unit beingsupplied by the necessary signals and current from the vessel at thesurface through conductor cable 67. The actuator unit is then eitherelectrically or hydraulically connected through power transmissionconduits 68 and 69 to the latch-down unit 60 and the blowout preventer42, respectively.

Since the present invention utilizes a dual conductor drill string, theswivel 20 (FIGURE must be provided with dual conduits 31 and 71 whichare in communication with dual conduits 21 and 21a respectively of thekelly section at the top of the drill string. The swivel head 26 isprovided with the usual type of bail 72 by which it is supported fromthe traveling block 19 (FIGURE 1). The outer section of kelly 21 may beconnected to the swivel by screw threads, as at 73 while the inner pipe21a of the kelly section may be provided with a slip joint and seal, asat 74. The mud hoses 31 and 71 may be provided with valves 75 and 76 atsome point in their length as desired.

Methods of connecting adjacent sections of concentric pipes 46 and 46a,to form the drill string of the present invention, may incorporate theuse of threads 77 on the outer pipe string 46 while the inner pipestring 46a employs a stab-type coupling or slip joint, as at 78 or viceversa. In the event that a stab-type coupling is employed, suitableseals such as O-ring seals 79 and 80 are used. In order to insure properspacing between the outer and inner pipe strings 46 and 46a, as well asto give additional strength to the drill string structure so thatthinner wall pipe may be used, a plurality of thin spacer lugs 81 arepositioned between the two pipes 46 and 46a and welded to at least oneof them. As shown in FIGURE 11, the

5 lugs 81 are welded to both the inner and outer pipe strings 46a and46, respectively. In FIGURE 12 the lugs 82 are welded only to the innerpipe string 46a since the sections of this type string are coupledtogether by means of screw threads, as at 83, while the outer string 46is threaded as at 84.

The lower end of a dual concentric dual string in accordance with thepresent invention is shown in FIGURE 13 as employing a dual-conduittelescoping joint or bumper sub 85 and a plurality of dual-conduit drillcollars 86. The bit 87 at the lower end thereof is provided with one ormore fluid circulation ports 88 in communication with the annular space89 between concentric pipe 46 and 46a forming the drill string, whichannular space extends down through the bumper sub 85 and the drillcollars 86. Drilling fluid is then circulated up through the centralopening (not shown) in the bottom of the bit 87 and up the inner pipestring 46a.

One form of a dual-conduit telescoping joint or bumper sub 85 is shownin FIGURE 15. The outwardly and inwardly-extending flanges 90 and 91,respectively, form stop means to limit the maximum extension of thetelescoping joint 85. At least one of the telescoping pipes is providedwith a splined section or is formed in a nonround configuration, as at92 so that the lower end of the telescoping joint will rotate whentorque is applied to the upper portion of the telescoping joint. It isto be understood that suitable seals 93 are provided between the telescoping pipe sections, as needed. Returning to FIGURE 4 of the drawing,drilling operations are resumed by lowering into the well the dualconduit drill string 46 having bit 87 at the lower end thereof. Duringdrilling the drilling mud is circulated by means of pump 30 through hose31 and swivel 20 down through kelly section 21 and preferably downthrough the annular space between the two pipe sections 46 and 46a(FIGURES 11 and 12) and out the drill bit 87 at the bottom of the hole28. The drilling fluid, together with the earth-formation cuttingsformed by the drill bit, would be forced up the inner pipe string 46a,through the inner kelly pipe 21:: (FIGURE 10) and out the discharge hose71 and into the mud settling tank 24. While this is the preferred methodof circulation it is to be understood that drilling operations can becarried out readily, especially in soft formations, by circulating thedrilling mud down the center pipe 46a and up the annular space betweenthe inner and outer pipes 56a and 46, respectively.

In the event that it is desired to change the flow within the twoconduits forming the drill string 46, a fluid flow crossover device maybe employed as shown in FIGURE 16. In this device a packer 94 is set inthe pipe string 46 around a special section of inner pipe string 46bwhich is provided with flow passageways 95 and 96 which causes fluid inthe annular space 89 above the packer 94 to be channeled into the innerpipe string 46a with similar action being taken place in handling theflow coming up the annular space 89 below the packer.

In order to obviate the use of a dual-conductor telescoping joint orbumper sub as shown in FIGURE 15, a telescoping joint or bumper sub 97(FIGURE 14) having a single central conduit 98 in communication with theinner pi-pe string 46a is preferably used. Thus, the annular space 89between the pipe strings 46 and 46a would be blanked oil in any suitablemanner as by a plate 99 while one or more fluid discharge ports 100 areprovided in the outer pipe string 46 so that fluid circulating down theannular space 89 would be discharged through the ports 100 and flowdownwardly around the telescoping joints 98 and drill collars 86 to washacross the cutting face of the bit 87, removing cuttings from the bottomof the hole and washing them up through the inner pipe string 46a.

While it is realized that the drilling of an underwater well may bestarted with a dual conduit drill string rather than a single conduitdrill string as described with regard to FIGURE 1, the dual conduitwould have to be pulled out of the well before cementing operations werecarried out therein as it would be too dangerous to attempt to circulatecement down through one of the two conduits of a dual conduit pipestring. If such an operation was to be carried out in an emergency, theother conduit would be maintained full of fluid so that no cement couldbe circulated up it.

Thus, after drilling the necessary amount of hole in accordance withFIGURE 4, prior to setting the next string of casing 101 (FIGURE thedual-conduit drill string would be pulled back to the vessel 11. Thecasing 101 would then be run down into the well being guided originallyinto .place by removable sealing unit 45 running along guide lines 35and 36 and being lowered into the well by means of a running or loweringpipe string 102 of small diameter which can be readily detached from thetop of the casing 101 when the latter is seated in the casinghead 44.Alternatively, the lower end of the casing 101 could be run in the wellin a manner shown and described in patent application Serial No.223,335, filed September 13, 1962. The running pipe string 102 couldthen be utilized as a cementing pipe string for circulating cement downinto the well to cement the casing 101 therein.

While the method and apparatus of the present invention have beendescribed hereinabove with regard to utilizing guide lines 35 and 36which extend between the vessel 11 and the drilling wellhead in order toguide pipe into the well, it is to be understood that any other suitableguide means could be employed. For example, in FIGURE 6 a guide rod 103is employed which is made up of sections of rod or small diameter pipeconnected together and adapted to extend down through the bit 104 andintothe well. As shown in FIGURE 6A, prior to pulling the bit 104(FIGURE 6) out of the well, the guide rod 103 is dropped down throughdrill string 46 and out the bit 104 except for a stop member 105 adaptedto seat itself on a pair of lugs 106 and 107 extending in from the innerwall of the inner pipe string 46a th guide rod 103 is also provided witha fishing head 108. The length of the guide rod 103 must be slightlygreater than the depth of the water between the vessel 11 and thewellhead on the ocean floor.

After dropping the guide rod down the pipe string 46 and having it landon the bottom of the hole or seat on the landing lugs 106 and 107, thedrill string 46 would then be withdrawn to the surface while the guiderod 103 would be drawn upwardly along with it. The lower end of theguide rod 103 would always maintain contact with the well. Thus, afterremoving the stop member 105 at the vessel the drill bit 104 could beremoved and a new bit installed on the top of the guide rod 103, beingremovably secured thereto by reattaching the stop member 105 to the topof the guide rod 103. The new bit and drill string 46 would then belowered into the well with the guide rod 103 moving down into the well.A wire-line fishing tool of any well known type would then be run downthrough the inner pipe string 46a to engage the fishing head 108 at thetop of the guide rod 103 so that the guide rod 103 could be pulled upthrough the drill string 46 to the vessel prior to carrying out furtherdrilling operations.

It may be seen that a method and apparatus have been provided fordrilling at deep-water locations where it would be otherwise impossibleto support the necessary length of marine conductor pipe or flexible mudhoses. At the same time, there has been provided a circulating mudsystem which is relatively more flexible than any presently known whileat the same time having a minimum area exposed to underwater currentsand wave forces at the surface. At the same time the weight of the drillstring in the well provides the tension necessary to maintain thecirculating mud and drill pipe in a substantially straight line betweenthe vessel and the well rather than the need for providing this tensionfrom the vessel at the surface.

Although the drilling operation has been described with regard to FIGURE4 as employing a dual-conduit 1.0 drill string extending from the vesselto the bit at the bottom of the well, it is to be understood that atsome locations, particularly when drilling through fairly wellconsolidated formations, the dual conduit string 46 may extend only fromthe vessel to a short distance below the sealing unit 45 and thewellhead assembly on the ocean floor. Drilling fluid would be circulateddown the annular space between the inner and outer conduits 46 and 46a(FIGURE 11) which would terminate below the sealing unit 45 (FIGURE 4)and from there to the bottom of the well the drilling fluid would becirculated outside a single conduit drill string 46 (FIGURE 17) to bereturned up the drill string along with the cuttings from the bottom ofthe well. In such an arrangement the single-conduit drill stringextending below the dualconduit drill string would be normal drill pipewhile the pipes making up the dual conduit section of the drill stringcould be thinner walled pipe. In drilling with this combination of asingle-conduit and dual-conduit drill string, every time a round tripwas made to change a bit on the drill string, normal single conduitdrill pipe would be run into the well with a new bit until the bit wasoil the bottom of the well a distance slightly greater than the epth ofthe water in which the drilling operations were being carried out. Atthis time dual-conduit drill pipe sections would be connected to the topof a single-conduit drill pipe and the entire drill string wouldcontinue to be lowered as made up until the lower end of the dualconduit drill string had passed through and was sealingly engaged by the.sealing'unit 45 at the wellhead. Thereafter, as drilling progressedadditional sections of dual conduit drill pipe would be connected to thetop of the drill string below the kelly.

We claim as our invention:

1. Apparatus for drilling an underwater well from a floating vesselpositioned at an offshore location, said apparatus comprising:

(a) a floating vessel;

(b) a drilling wellhead structure positioned below the surface of thewater beneath said vessel, said wellhead structure having a verticalthroughbore aligned with a well in the ocean floor;

(c) a drill string adapted to extend from said vessel and into thethroughbore of said wellhead structure;

(d) packer means adapted to be in operative sealing engagement betweensaid wellhead structure and the outer surface of said drill string toseal the throughbore of said wellhead structure about said drill stringand prevent all fluid from leaving the Well except through said drillstring;

(e) said drill string having multiple conduit means at least extendingfrom a point adjacent said vessel to a point below said packer means ofsaid wellhead structure; and

(f) said multiple conduit means being simultaneously rotatable togetherand axially slidable through said packer means while remaining insubstantial sealing engagement therewith during drilling operations.

2. The apparatus of claim 1 wherein said dual conduit drill stringincludes a dual conduit telescoping section.

3. The apparatus of claim 1 wherein the length and weight of the drillstring extending below the wellhead 1S sufficient to maintain adequatetension on said drill string to maintain it in a substantially verticalposition beneath said vessel.

4. The apparatus of claim 1 wherein the conduit means of the drillstring comprises two concentric pipe strings secured together in spacedrelationship whereby a flow passage is formed between. the two pipes anda drill bit is connected to the lower end of the drill string.

5. The apparatus of claim 4 wherein both of the concentric pipe stringsextend to a bit at the bottom of the drill string, said bit beingprovided with at least one fluid port through the body thereof incommunication with the space between said concentric pipe strings, andat least a second fluid port in communication between 11 the bore of theinner pipe string and the space outside the bit.

6. The apparatus of claim wherein said second fluid port is centrallylocated in said bit and is of a size to permit earth formation cuttingsto enter the inner string of said concentric pipe strings.

7. The apparatus of claim 1 including a dual conduit kelly sectioncoupled to the upper end of said dual conduit drill string.

8. The apparatus of claim 7 wherein the dual conduits of said kelly arearranged concentrically and extend longitudinally through said kelly.

9. The apparatus of claim 1 wherein said dual conduit drill stringcomprises dual conduit pipe extending from a point adjacent the vesseldown to and being secured to a plurality of drill collars having asingle conduit therethrough adapted to communicate with only one of saidconduits of said dual conduit pipe, there being outlet fluid port meansthrough the wall of said pipe to the outside in communication with theother conduit of said dual conduit pipe above said drill collars, and adrill bit attached to the lowermost drill collar.

10. The apparatus of claim 9 including a telescoping section in saiddrill string with at least one drill colla of said drill stringpositioned above it.

11. The apparatus of claim 1 including guide means adapted to be inoperative engagement between the lower end of :the drill string and thewellhead structure.

12. The apparatus of claim 11 wherein said guide means includes guidelines extending from said vessel to said wellhead structure and meansslidably mounted near the lower end of said drill string and slidablymounted on said guide lines for aligning the lower end of said drillstring with the throughbore of said wellhead structure.

13. Apparatus for drilling an underwater well from a floating vesselpositioned at an oifshore location, said apparatus comprising:

(a) a floating vessel;

(b) a drilling Wellhead structure positioned below the surface of thewater beneath said vessel, said wellhead structure having a verticalthroughbore aligned with a well in the ocean floor;

(c) a drill string adapted to extend from said vessel and into thethroughbore of said Wellhead structure;

(d) packer means adapted to be in operative sealing engagement betweensaid wellhead structure and the outer surface of said drill string toseal the throughbore of said wellhead structure about said drill string;

(e) said drill string having multiple conduit means at least extendingfrom a point adjacent said vessel to a point below said packer means ofsaid wellhead structure; and

(f) said multiple conduit means being simultaneously rotatable togetherand axially slidable through said packer means while remaining insubstantial sealing engagement therewith during drilling operations,

(g) the conduit means of the drill string comprises two concentric pipestrings secured together in spaced relationship whereby a flow passageis formed between the two pipes and a drill bit is connected to thelower end of the drill string,

(h) the outer concentric pipe string extending from a point adjacent thevessel to a point just below the pack-er means at said wellheadstructure and the inner pipe string only is provided with a drill bit atits lower end adapted to drill at least the upper portion of a well of adiameter greater than that of the outer pipe.

References Cited by the Examiner UNITED STATES PATENTS 2,543,382 2/1951Schabarum -215 X 2,663,545 12/1953 Grable 175-215 X 2,701,122 2/1955Grable 175-69 2,808,229 10/1957 Bauer et a1. 175-7 2,849,213 8/1958Failing 175-215 X 2,850,264 9/ 1958 Grable.

3,065,807 11/1962 Wells 175-321 3,102,600 9/1963 Jackson 175-2153,163,238 12/1964 Malott 175-5 CHARLES E. OCONNELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner.

1. APPARATUS FOR DRILLING AN UNDERWATER WELL FROM A FLOATING VESSELPOSITIONED AT AN OFFSHORE LOCATION, SAID APPARATUS COMPRISING: (A) AFLOATING VESSEL: (B) A DRILLING WELLHEAD STRUCTURE POSITIONED BELOW THESURFACE OF THE WATER BENEATH SAID VESSEL, SAID WELLHEAD STRUCTURE HAVINGA VERTICAL THROUGHBORE ALIGNED WITH A WELL IN THE OCEAN FLOOR; (C) ADRILL STRING ADAPTED TO EXTEND FROM SAID VESSEL (D) PACKER MEANS ADAPTEDTO BE IN OPERATIVE SEALING ENGAGEMENT BETWEEN SAID WELLHEAD STRUCTUREAND THE ENGAGEMENT BETWEEN SAID WELLHEAD STRUCTURE AND THE OUTER SURFACEOF SAID DRILL STRING TO SEAL THE THROUGHBORE OF SAID WELLHEAD STRUCTUREABOUT SAID DRILL STRING AND PREVENT ALL FLUID FROM LEAVING THE WELLEXCEPT THROUGH SAID DRILL STRING; (E) SAID DRILL STRING HAVING MULTIPLECONDUIT MEANS AT LEAST EXTENDING FROM A POINT ADJACENT SAID VESSEL TO APOINT BELOW SAID PACKER MEANS OF SAID WELLHEAD STRUCTURE; AND (F) SAIDMULTIPLE CONDUIT MEANS BEING SIMULTANEOUSLY ROTATABLE TOGETHER ANDAXIALLY SUBSTANTIAL SEALING PACKET MEANS WHILE REMAINING IN SUBSTANTIALSEALING ENGAGEMENT THEREWITH DURING DRILLING OPERATIONS.